The invention concerns a device for the angular adjustment of a camshaft relative to a crankshaft of an internal combustion piston engine, particularly a vane-type adjuster comprising a stator and a rotor arranged coaxially to the stator, vanes of the rotor being pivotable by oil pressure in pressure chambers defined by radial walls of the stator.
A generic vane-type adjuster of the pre-cited type is known from DE 196 23 818 A1. Here, too, the stator that is operatively connected to the crankshaft defines with its radially extending walls, pressure chambers in which the vanes of the rotor can be pivoted relative to the stator by oil pressure. This results in the desired angular adjustment of the camshaft relative to the crankshaft.
The stator and the rotor can be made by sinter pressing but due to the diameter and cross-section ratios, this is only possible with complicated and cost-intensive refinishing. In addition to this, appropriate oil channels have to be provided in the rotor for the actuation of the individual pressure chambers. These channels can either be formed integrally during the sintering operation or have to be made by subsequent machining. While the oil channels made during the sintering operation are situated on the lateral surfaces of the rotor and lead to a deterioration of sealing properties, the channels made by machining cause additional manufacturing work.
The object of the invention is to reduce the work involved in the manufacture of a vane-type adjuster of a camshaft.
The invention achieves the above object with a device wherein the stator and the rotor are comprised respectively of a stack of stator blanks and a stack of rotor blanks, said blanks are made preferably by punching and are firmly connected to one another. The so-called punching and stacking technology used here originates from the field of construction of alternating current apparatuses where it serves to suppress eddy currents. Assembled camshafts with cams composed of identical blanks are also known.
In the device of the invention, the punching and stacking technology is used on hydraulic components of camshaft adjusters. The punching of the individual blanks and their firm connection to one another to form stacks are operations that can be automated and result in ready-to-be-installed components with a relatively small amount of fabrication work.
In an advantageous embodiment of the invention, the blanks have an identical outer contour but some of them have additional punched-out regions inside the outer contour and a defined position in the respective stack of blanks. Due to the identical outer contour of the individual blanks, the stack has the outer appearance of a homogeneous component. The blanks that have the additional punched-out regions inside the outer contour and are arranged in a defined position, form hollow inner spaces or channels that do not require any refinishing and do not cause any additional internal leakage.
Advantageously, particularly individual rotor blanks comprise either registering or offset, preferably radial punched-out regions which, when combined with rotor blanks without such regions, define laterally closed channels. In this way, the oil channels required for actuating the individual pressure chambers can be realized in the rotor with a small amount of work and with low leakage. The offset radial channels that are formed by the offset punched-out regions provided in a plurality of sheet metal layers enhance the stability and the shape quality of the individual blanks. Besides this, a greater flexibility in designing the oil channels is obtained that may be required in practical use.
In a further advantageous embodiment of the invention, the blanks comprise punched-out regions of identical shape, angular position and distance from the center and form an axial through-hole or, in combination with at least one blank without punched-out regions, they form at least one axial pocket hole. In this way, for example, the pocket bore required for a locking mechanism of the adjuster or a stepped central bore for the camshaft can be made in the rotor, and through-bores for tightening screws, in the stator.
It has proved to be of advantage to connect the blanks to one another, for example, by laser welding, stamping, gluing, countersunk riveting, countersunk screwing or by combinations of these joining methods. In this way, the stacks of blanks of the stator and the rotor become irreversibly joined components.
If registering punched recesses are made preferably on the outer contour of the blanks and laser welding is performed in the bottom region of these recesses, the weld zone is not affected by a possibly required post-machining.
In an advantageous embodiment of the invention, in place of countersinking a countersunk bore for countersunk head rivets, stepped punching is effected on at least two blanks on each side of the stator and the rotor, preferably with adjustable punching tools. This constitutes an inexpensive substitute for countersinking because no post-machining is required.
To obtain components with exact dimensions and achieve a good utilization of the sheet metal strip, it is advantageous to punch out the stator blanks and the rotor blanks in a coaxial arrangement out of a precision sheet metal strip. In this way, post-machining (e.g. grinding of height, outer and inner diameter) can be minimized or even eliminated. Due to the small thickness tolerances of the sheet metal strip, the punched and stacked parts have substantially the same quality as finished products. Strip thicknesses of 0.5 to 1.5 mm have the advantage that certain dimensions can be obtained by combining appropriate sheet thicknesses. Steel and aluminium have proved to be the most advantageous base materials for the sheet metal strips.
Oil leak tightness of the rotors and stators can be achieved by arranging flat seals between the individual blanks or by coating the blanks with a soft material. Without a sealing material between the blanks, the aforesaid joining methods result in the formation of fine fissures that can result in a certain amount of leakage. This can be desirable from the lubrication point of view.
Further features of the invention will become obvious from the following description of the drawings and from the drawings themselves in which one example of embodiment is schematically represented.